[PATCH] mm: introduce dump_page() and print symbolic flag names

[PATCH] mm: introduce dump_page() and print symbolic flag names

[Wu Fengguang]

- introduce dump_page() to print the page info for debugging some error condition.
- convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
- print an extra field: the symbolic names of page->flags

Example dump_page() output:

[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:147
[  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)

CC: Ingo Molnar <mingo@elte.hu> 
CC: Alex Chiang <achiang@hp.com>
CC: Rik van Riel <riel@redhat.com>
CC: Andi Kleen <andi@firstfloor.org> 
CC: Mel Gorman <mel@linux.vnet.ibm.com> 
CC: Christoph Lameter <cl@linux-foundation.org> 
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/linux/mm.h  |    2 +
 mm/memory.c         |    8 +---
 mm/memory_hotplug.c |    6 +--
 mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
 4 files changed, 86 insertions(+), 13 deletions(-)

--- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/page_alloc.c	2009-12-16 20:17:18.000000000 +0800
@@ -49,6 +49,7 @@
 #include <linux/debugobjects.h>
 #include <linux/kmemleak.h>
 #include <trace/events/kmem.h>
+#include <linux/ftrace_event.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -262,10 +263,7 @@ static void bad_page(struct page *page)
 
 	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
-	printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
+	dump_page(page);
 
 	dump_stack();
 out:
@@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
 	return order < MAX_ORDER;
 }
 #endif
+
+static struct trace_print_flags pageflag_names[] = {
+	{1UL << PG_locked,		"locked"	},
+	{1UL << PG_error,		"error"		},
+	{1UL << PG_referenced,		"referenced"	},
+	{1UL << PG_uptodate,		"uptodate"	},
+	{1UL << PG_dirty,		"dirty"		},
+	{1UL << PG_lru,			"lru"		},
+	{1UL << PG_active,		"active"	},
+	{1UL << PG_slab,		"slab"		},
+	{1UL << PG_owner_priv_1,	"owner_priv_1"	},
+	{1UL << PG_arch_1,		"arch_1"	},
+	{1UL << PG_reserved,		"reserved"	},
+	{1UL << PG_private,		"private"	},
+	{1UL << PG_private_2,		"private_2"	},
+	{1UL << PG_writeback,		"writeback"	},
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+	{1UL << PG_head,		"head"		},
+	{1UL << PG_tail,		"tail"		},
+#else
+	{1UL << PG_compound,		"compound"	},
+#endif
+	{1UL << PG_swapcache,		"swapcache"	},
+	{1UL << PG_mappedtodisk,	"mappedtodisk"	},
+	{1UL << PG_reclaim,		"reclaim"	},
+	{1UL << PG_buddy,		"buddy"		},
+	{1UL << PG_swapbacked,		"swapbacked"	},
+	{1UL << PG_unevictable,		"unevictable"	},
+#ifdef CONFIG_MMU
+	{1UL << PG_mlocked,		"mlocked"	},
+#endif
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
+	{1UL << PG_uncached,		"uncached"	},
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+	{1UL << PG_hwpoison,		"hwpoison"	},
+#endif
+	{-1UL,				NULL		},
+};
+
+static void dump_page_flags(unsigned long flags)
+{
+	const char *delim = "";
+	unsigned long mask;
+	int i;
+
+	printk(KERN_ALERT "page flags: %lx(", flags);
+
+	/* remove zone id */
+	flags &= (1UL << NR_PAGEFLAGS) - 1;
+
+	for (i = 0; pageflag_names[i].name && flags; i++) {
+
+		mask = pageflag_names[i].mask;
+		if ((flags & mask) != mask)
+			continue;
+
+		flags &= ~mask;
+		printk("%s%s", delim, pageflag_names[i].name);
+		delim = "|";
+	}
+
+	/* check for left over flags */
+	if (flags)
+		printk("%s%#lx", delim, flags);
+
+	printk(")\n");
+}
+
+void dump_page(struct page *page)
+{
+	printk(KERN_ALERT
+	       "page:%p count:%d mapcount:%d mapping:%p index:%lx\n",
+		page, page_count(page), page_mapcount(page),
+		page->mapping, page->index);
+	dump_page_flags(page->flags);
+}
--- linux-mm.orig/mm/memory.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory.c	2009-12-14 19:21:22.000000000 +0800
@@ -430,12 +430,8 @@ static void print_bad_pte(struct vm_area
 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
 		current->comm,
 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
-	if (page) {
-		printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
-	}
+	if (page)
+		dump_page(page);
 	printk(KERN_ALERT
 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
--- linux-mm.orig/mm/memory_hotplug.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory_hotplug.c	2009-12-14 19:21:22.000000000 +0800
@@ -678,9 +678,9 @@ do_migrate_range(unsigned long start_pfn
 			if (page_count(page))
 				not_managed++;
 #ifdef CONFIG_DEBUG_VM
-			printk(KERN_INFO "removing from LRU failed"
-					 " %lx/%d/%lx\n",
-				pfn, page_count(page), page->flags);
+			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+			       pfn);
+			dump_page(page);
 #endif
 		}
 	}
--- linux-mm.orig/include/linux/mm.h	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/include/linux/mm.h	2009-12-14 19:21:22.000000000 +0800
@@ -1328,5 +1328,7 @@ extern void shake_page(struct page *p, i
 extern atomic_long_t mce_bad_pages;
 extern int soft_offline_page(struct page *page, int flags);
 
+extern void dump_page(struct page *page);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

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Re: [PATCH] mm: introduce dump_page() and print symbolic flag names

[Wu Fengguang]

On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
> - introduce dump_page() to print the page info for debugging some error condition.
> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
> - print an extra field: the symbolic names of page->flags
> 
> Example dump_page() output:
> 
> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1
> mapping:ffff88001c901791 index:147
                                 ~~~ this is in fact 0x147

The index value may sometimes be misread as decimal number, shall this
be fixed by adding a "0x" prefix?

> [  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)

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Re: [PATCH] mm: introduce dump_page() and print symbolic flag names

[Américo Wang]

On Wed, Dec 16, 2009 at 08:33:10PM +0800, Wu Fengguang wrote:
>On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
>> - introduce dump_page() to print the page info for debugging some error condition.
>> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
>> - print an extra field: the symbolic names of page->flags
>> 
>> Example dump_page() output:
>> 
>> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1
>> mapping:ffff88001c901791 index:147
>                                 ~~~ this is in fact 0x147
>
>The index value may sometimes be misread as decimal number, shall this
>be fixed by adding a "0x" prefix?


Using '%#x' will do.

Thanks.


>
>> [  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)
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[PATCH v2] mm: introduce dump_page() and print symbolic flag names

[Wu Fengguang]

On Wed, Dec 16, 2009 at 11:35:13PM +0800, AmA(C)rico Wang wrote:
> On Wed, Dec 16, 2009 at 08:33:10PM +0800, Wu Fengguang wrote:
> >On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
> >> - introduce dump_page() to print the page info for debugging some error condition.
> >> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
> >> - print an extra field: the symbolic names of page->flags
> >> 
> >> Example dump_page() output:
> >> 
> >> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1
> >> mapping:ffff88001c901791 index:147
> >                                 ~~~ this is in fact 0x147
> >
> >The index value may sometimes be misread as decimal number, shall this
> >be fixed by adding a "0x" prefix?
> 
> 
> Using '%#x' will do.

Thanks, here is the updated patch.
---
mm: introduce dump_page()

- introduce dump_page() to print the page info for debugging some error condition.
- convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
- print an extra field: the symbolic names of page->flags

Example dump_page() output:

[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:0x147
[  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)

CC: Ingo Molnar <mingo@elte.hu> 
CC: Alex Chiang <achiang@hp.com>
CC: Rik van Riel <riel@redhat.com>
CC: Andi Kleen <andi@firstfloor.org> 
CC: Mel Gorman <mel@linux.vnet.ibm.com> 
CC: Christoph Lameter <cl@linux-foundation.org> 
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/linux/mm.h  |    2 +
 mm/memory.c         |    8 +---
 mm/memory_hotplug.c |    6 +--
 mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
 4 files changed, 86 insertions(+), 13 deletions(-)

--- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/page_alloc.c	2009-12-16 20:33:35.000000000 +0800
@@ -49,6 +49,7 @@
 #include <linux/debugobjects.h>
 #include <linux/kmemleak.h>
 #include <trace/events/kmem.h>
+#include <linux/ftrace_event.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -262,10 +263,7 @@ static void bad_page(struct page *page)
 
 	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
-	printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
+	dump_page(page);
 
 	dump_stack();
 out:
@@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
 	return order < MAX_ORDER;
 }
 #endif
+
+static struct trace_print_flags pageflag_names[] = {
+	{1UL << PG_locked,		"locked"	},
+	{1UL << PG_error,		"error"		},
+	{1UL << PG_referenced,		"referenced"	},
+	{1UL << PG_uptodate,		"uptodate"	},
+	{1UL << PG_dirty,		"dirty"		},
+	{1UL << PG_lru,			"lru"		},
+	{1UL << PG_active,		"active"	},
+	{1UL << PG_slab,		"slab"		},
+	{1UL << PG_owner_priv_1,	"owner_priv_1"	},
+	{1UL << PG_arch_1,		"arch_1"	},
+	{1UL << PG_reserved,		"reserved"	},
+	{1UL << PG_private,		"private"	},
+	{1UL << PG_private_2,		"private_2"	},
+	{1UL << PG_writeback,		"writeback"	},
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+	{1UL << PG_head,		"head"		},
+	{1UL << PG_tail,		"tail"		},
+#else
+	{1UL << PG_compound,		"compound"	},
+#endif
+	{1UL << PG_swapcache,		"swapcache"	},
+	{1UL << PG_mappedtodisk,	"mappedtodisk"	},
+	{1UL << PG_reclaim,		"reclaim"	},
+	{1UL << PG_buddy,		"buddy"		},
+	{1UL << PG_swapbacked,		"swapbacked"	},
+	{1UL << PG_unevictable,		"unevictable"	},
+#ifdef CONFIG_MMU
+	{1UL << PG_mlocked,		"mlocked"	},
+#endif
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
+	{1UL << PG_uncached,		"uncached"	},
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+	{1UL << PG_hwpoison,		"hwpoison"	},
+#endif
+	{-1UL,				NULL		},
+};
+
+static void dump_page_flags(unsigned long flags)
+{
+	const char *delim = "";
+	unsigned long mask;
+	int i;
+
+	printk(KERN_ALERT "page flags: %lx(", flags);
+
+	/* remove zone id */
+	flags &= (1UL << NR_PAGEFLAGS) - 1;
+
+	for (i = 0; pageflag_names[i].name && flags; i++) {
+
+		mask = pageflag_names[i].mask;
+		if ((flags & mask) != mask)
+			continue;
+
+		flags &= ~mask;
+		printk("%s%s", delim, pageflag_names[i].name);
+		delim = "|";
+	}
+
+	/* check for left over flags */
+	if (flags)
+		printk("%s%#lx", delim, flags);
+
+	printk(")\n");
+}
+
+void dump_page(struct page *page)
+{
+	printk(KERN_ALERT
+	       "page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
+		page, page_count(page), page_mapcount(page),
+		page->mapping, page->index);
+	dump_page_flags(page->flags);
+}
--- linux-mm.orig/mm/memory.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory.c	2009-12-14 19:21:22.000000000 +0800
@@ -430,12 +430,8 @@ static void print_bad_pte(struct vm_area
 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
 		current->comm,
 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
-	if (page) {
-		printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
-	}
+	if (page)
+		dump_page(page);
 	printk(KERN_ALERT
 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
--- linux-mm.orig/mm/memory_hotplug.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory_hotplug.c	2009-12-14 19:21:22.000000000 +0800
@@ -678,9 +678,9 @@ do_migrate_range(unsigned long start_pfn
 			if (page_count(page))
 				not_managed++;
 #ifdef CONFIG_DEBUG_VM
-			printk(KERN_INFO "removing from LRU failed"
-					 " %lx/%d/%lx\n",
-				pfn, page_count(page), page->flags);
+			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+			       pfn);
+			dump_page(page);
 #endif
 		}
 	}
--- linux-mm.orig/include/linux/mm.h	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/include/linux/mm.h	2009-12-14 19:21:22.000000000 +0800
@@ -1328,5 +1328,7 @@ extern void shake_page(struct page *p, i
 extern atomic_long_t mce_bad_pages;
 extern int soft_offline_page(struct page *page, int flags);
 
+extern void dump_page(struct page *page);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

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Re: [PATCH v2] mm: introduce dump_page() and print symbolic flag names

[KOSAKI Motohiro]

> On Wed, Dec 16, 2009 at 11:35:13PM +0800, AmA(C)rico Wang wrote:
> > On Wed, Dec 16, 2009 at 08:33:10PM +0800, Wu Fengguang wrote:
> > >On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
> > >> - introduce dump_page() to print the page info for debugging some error condition.
> > >> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
> > >> - print an extra field: the symbolic names of page->flags
> > >> 
> > >> Example dump_page() output:
> > >> 
> > >> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1
> > >> mapping:ffff88001c901791 index:147
> > >                                 ~~~ this is in fact 0x147
> > >
> > >The index value may sometimes be misread as decimal number, shall this
> > >be fixed by adding a "0x" prefix?
> > 
> > 
> > Using '%#x' will do.
> 
> Thanks, here is the updated patch.
> ---
> mm: introduce dump_page()
> 
> - introduce dump_page() to print the page info for debugging some error condition.
> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
> - print an extra field: the symbolic names of page->flags
> 
> Example dump_page() output:
> 
> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:0x147
> [  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)
> 
> CC: Ingo Molnar <mingo@elte.hu> 
> CC: Alex Chiang <achiang@hp.com>
> CC: Rik van Riel <riel@redhat.com>
> CC: Andi Kleen <andi@firstfloor.org> 
> CC: Mel Gorman <mel@linux.vnet.ibm.com> 
> CC: Christoph Lameter <cl@linux-foundation.org> 
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
>  include/linux/mm.h  |    2 +
>  mm/memory.c         |    8 +---
>  mm/memory_hotplug.c |    6 +--
>  mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
>  4 files changed, 86 insertions(+), 13 deletions(-)
> 
> --- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
> +++ linux-mm/mm/page_alloc.c	2009-12-16 20:33:35.000000000 +0800
> @@ -49,6 +49,7 @@
>  #include <linux/debugobjects.h>
>  #include <linux/kmemleak.h>
>  #include <trace/events/kmem.h>
> +#include <linux/ftrace_event.h>
>  
>  #include <asm/tlbflush.h>
>  #include <asm/div64.h>
> @@ -262,10 +263,7 @@ static void bad_page(struct page *page)
>  
>  	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
>  		current->comm, page_to_pfn(page));
> -	printk(KERN_ALERT
> -		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
> -		page, (void *)page->flags, page_count(page),
> -		page_mapcount(page), page->mapping, page->index);
> +	dump_page(page);
>  
>  	dump_stack();
>  out:
> @@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
>  	return order < MAX_ORDER;
>  }
>  #endif
> +
> +static struct trace_print_flags pageflag_names[] = {
> +	{1UL << PG_locked,		"locked"	},
> +	{1UL << PG_error,		"error"		},
> +	{1UL << PG_referenced,		"referenced"	},
> +	{1UL << PG_uptodate,		"uptodate"	},
> +	{1UL << PG_dirty,		"dirty"		},
> +	{1UL << PG_lru,			"lru"		},
> +	{1UL << PG_active,		"active"	},
> +	{1UL << PG_slab,		"slab"		},
> +	{1UL << PG_owner_priv_1,	"owner_priv_1"	},
> +	{1UL << PG_arch_1,		"arch_1"	},
> +	{1UL << PG_reserved,		"reserved"	},
> +	{1UL << PG_private,		"private"	},
> +	{1UL << PG_private_2,		"private_2"	},
> +	{1UL << PG_writeback,		"writeback"	},
> +#ifdef CONFIG_PAGEFLAGS_EXTENDED
> +	{1UL << PG_head,		"head"		},
> +	{1UL << PG_tail,		"tail"		},
> +#else
> +	{1UL << PG_compound,		"compound"	},
> +#endif
> +	{1UL << PG_swapcache,		"swapcache"	},
> +	{1UL << PG_mappedtodisk,	"mappedtodisk"	},
> +	{1UL << PG_reclaim,		"reclaim"	},
> +	{1UL << PG_buddy,		"buddy"		},
> +	{1UL << PG_swapbacked,		"swapbacked"	},
> +	{1UL << PG_unevictable,		"unevictable"	},
> +#ifdef CONFIG_MMU
> +	{1UL << PG_mlocked,		"mlocked"	},
> +#endif
> +#ifdef CONFIG_ARCH_USES_PG_UNCACHED
> +	{1UL << PG_uncached,		"uncached"	},
> +#endif
> +#ifdef CONFIG_MEMORY_FAILURE
> +	{1UL << PG_hwpoison,		"hwpoison"	},
> +#endif
> +	{-1UL,				NULL		},
> +};
> +
> +static void dump_page_flags(unsigned long flags)
> +{
> +	const char *delim = "";
> +	unsigned long mask;
> +	int i;
> +
> +	printk(KERN_ALERT "page flags: %lx(", flags);

nit.
Now, you append 0x prefix to index. why don't you appent 0x prefix to this?
I mean we have to keep consist prefix printing rule in the same printk.



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[PATCH v3] mm: introduce dump_page() and print symbolic flag names

[Wu Fengguang]

On Fri, Dec 18, 2009 at 09:35:59AM +0800, KOSAKI Motohiro wrote:
> > On Wed, Dec 16, 2009 at 11:35:13PM +0800, AmA(C)rico Wang wrote:
> > > On Wed, Dec 16, 2009 at 08:33:10PM +0800, Wu Fengguang wrote:
> > > >On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
> > > >> - introduce dump_page() to print the page info for debugging some error condition.
> > > >> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
> > > >> - print an extra field: the symbolic names of page->flags
> > > >> 
> > > >> Example dump_page() output:
> > > >> 
> > > >> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1
> > > >> mapping:ffff88001c901791 index:147
> > > >                                 ~~~ this is in fact 0x147
> > > >
> > > >The index value may sometimes be misread as decimal number, shall this
> > > >be fixed by adding a "0x" prefix?
> > > 
> > > 
> > > Using '%#x' will do.
> > 
> > +	printk(KERN_ALERT "page flags: %lx(", flags);
> 
> nit.
> Now, you append 0x prefix to index. why don't you appent 0x prefix to this?
> I mean we have to keep consist prefix printing rule in the same printk.

Good suggestion, thanks!
---

mm: introduce dump_page()

- introduce dump_page() to print the page info for debugging some error condition.
- convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
- print an extra field: the symbolic names of page->flags

Example dump_page() output:

[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:0x147
[  157.525570] page flags: 0x100000000100068(uptodate|lru|active|swapbacked)

CC: Ingo Molnar <mingo@elte.hu> 
CC: Alex Chiang <achiang@hp.com>
CC: Rik van Riel <riel@redhat.com>
CC: Andi Kleen <andi@firstfloor.org> 
CC: Mel Gorman <mel@linux.vnet.ibm.com> 
CC: Christoph Lameter <cl@linux-foundation.org> 
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/linux/mm.h  |    2 +
 mm/memory.c         |    8 +---
 mm/memory_hotplug.c |    6 +--
 mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
 4 files changed, 86 insertions(+), 13 deletions(-)

--- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/page_alloc.c	2009-12-18 10:08:24.000000000 +0800
@@ -49,6 +49,7 @@
 #include <linux/debugobjects.h>
 #include <linux/kmemleak.h>
 #include <trace/events/kmem.h>
+#include <linux/ftrace_event.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -262,10 +263,7 @@ static void bad_page(struct page *page)
 
 	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
-	printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
+	dump_page(page);
 
 	dump_stack();
 out:
@@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
 	return order < MAX_ORDER;
 }
 #endif
+
+static struct trace_print_flags pageflag_names[] = {
+	{1UL << PG_locked,		"locked"	},
+	{1UL << PG_error,		"error"		},
+	{1UL << PG_referenced,		"referenced"	},
+	{1UL << PG_uptodate,		"uptodate"	},
+	{1UL << PG_dirty,		"dirty"		},
+	{1UL << PG_lru,			"lru"		},
+	{1UL << PG_active,		"active"	},
+	{1UL << PG_slab,		"slab"		},
+	{1UL << PG_owner_priv_1,	"owner_priv_1"	},
+	{1UL << PG_arch_1,		"arch_1"	},
+	{1UL << PG_reserved,		"reserved"	},
+	{1UL << PG_private,		"private"	},
+	{1UL << PG_private_2,		"private_2"	},
+	{1UL << PG_writeback,		"writeback"	},
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+	{1UL << PG_head,		"head"		},
+	{1UL << PG_tail,		"tail"		},
+#else
+	{1UL << PG_compound,		"compound"	},
+#endif
+	{1UL << PG_swapcache,		"swapcache"	},
+	{1UL << PG_mappedtodisk,	"mappedtodisk"	},
+	{1UL << PG_reclaim,		"reclaim"	},
+	{1UL << PG_buddy,		"buddy"		},
+	{1UL << PG_swapbacked,		"swapbacked"	},
+	{1UL << PG_unevictable,		"unevictable"	},
+#ifdef CONFIG_MMU
+	{1UL << PG_mlocked,		"mlocked"	},
+#endif
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
+	{1UL << PG_uncached,		"uncached"	},
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+	{1UL << PG_hwpoison,		"hwpoison"	},
+#endif
+	{-1UL,				NULL		},
+};
+
+static void dump_page_flags(unsigned long flags)
+{
+	const char *delim = "";
+	unsigned long mask;
+	int i;
+
+	printk(KERN_ALERT "page flags: %#lx(", flags);
+
+	/* remove zone id */
+	flags &= (1UL << NR_PAGEFLAGS) - 1;
+
+	for (i = 0; pageflag_names[i].name && flags; i++) {
+
+		mask = pageflag_names[i].mask;
+		if ((flags & mask) != mask)
+			continue;
+
+		flags &= ~mask;
+		printk("%s%s", delim, pageflag_names[i].name);
+		delim = "|";
+	}
+
+	/* check for left over flags */
+	if (flags)
+		printk("%s%#lx", delim, flags);
+
+	printk(")\n");
+}
+
+void dump_page(struct page *page)
+{
+	printk(KERN_ALERT
+	       "page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
+		page, page_count(page), page_mapcount(page),
+		page->mapping, page->index);
+	dump_page_flags(page->flags);
+}
--- linux-mm.orig/mm/memory.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory.c	2009-12-14 19:21:22.000000000 +0800
@@ -430,12 +430,8 @@ static void print_bad_pte(struct vm_area
 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
 		current->comm,
 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
-	if (page) {
-		printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
-	}
+	if (page)
+		dump_page(page);
 	printk(KERN_ALERT
 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
--- linux-mm.orig/mm/memory_hotplug.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory_hotplug.c	2009-12-14 19:21:22.000000000 +0800
@@ -678,9 +678,9 @@ do_migrate_range(unsigned long start_pfn
 			if (page_count(page))
 				not_managed++;
 #ifdef CONFIG_DEBUG_VM
-			printk(KERN_INFO "removing from LRU failed"
-					 " %lx/%d/%lx\n",
-				pfn, page_count(page), page->flags);
+			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+			       pfn);
+			dump_page(page);
 #endif
 		}
 	}
--- linux-mm.orig/include/linux/mm.h	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/include/linux/mm.h	2009-12-14 19:21:22.000000000 +0800
@@ -1328,5 +1328,7 @@ extern void shake_page(struct page *p, i
 extern atomic_long_t mce_bad_pages;
 extern int soft_offline_page(struct page *page, int flags);
 
+extern void dump_page(struct page *page);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

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[PATCH v3] mm: introduce dump_page() and print symbolic flag names

[Wu Fengguang]

On Fri, Dec 18, 2009 at 09:35:59AM +0800, KOSAKI Motohiro wrote:
> > On Wed, Dec 16, 2009 at 11:35:13PM +0800, AmA(C)rico Wang wrote:
> > > On Wed, Dec 16, 2009 at 08:33:10PM +0800, Wu Fengguang wrote:
> > > >On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
> > > >> - introduce dump_page() to print the page info for debugging some error condition.
> > > >> - convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
> > > >> - print an extra field: the symbolic names of page->flags
> > > >> 
> > > >> Example dump_page() output:
> > > >> 
> > > >> [  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1
> > > >> mapping:ffff88001c901791 index:147
> > > >                                 ~~~ this is in fact 0x147
> > > >
> > > >The index value may sometimes be misread as decimal number, shall this
> > > >be fixed by adding a "0x" prefix?
> > > 
> > > 
> > > Using '%#x' will do.
> > 
> > +	printk(KERN_ALERT "page flags: %lx(", flags);
> 
> nit.
> Now, you append 0x prefix to index. why don't you appent 0x prefix to this?
> I mean we have to keep consist prefix printing rule in the same printk.

Good suggestion, thanks!
---

mm: introduce dump_page()

- introduce dump_page() to print the page info for debugging some error condition.
- convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
- print an extra field: the symbolic names of page->flags

Example dump_page() output:

[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:0x147
[  157.525570] page flags: 0x100000000100068(uptodate|lru|active|swapbacked)

CC: Ingo Molnar <mingo@elte.hu> 
CC: Alex Chiang <achiang@hp.com>
CC: Rik van Riel <riel@redhat.com>
CC: Andi Kleen <andi@firstfloor.org> 
CC: Mel Gorman <mel@linux.vnet.ibm.com> 
CC: Christoph Lameter <cl@linux-foundation.org> 
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/linux/mm.h  |    2 +
 mm/memory.c         |    8 +---
 mm/memory_hotplug.c |    6 +--
 mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
 4 files changed, 86 insertions(+), 13 deletions(-)

--- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/page_alloc.c	2009-12-18 10:08:24.000000000 +0800
@@ -49,6 +49,7 @@
 #include <linux/debugobjects.h>
 #include <linux/kmemleak.h>
 #include <trace/events/kmem.h>
+#include <linux/ftrace_event.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -262,10 +263,7 @@ static void bad_page(struct page *page)
 
 	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
-	printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
+	dump_page(page);
 
 	dump_stack();
 out:
@@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
 	return order < MAX_ORDER;
 }
 #endif
+
+static struct trace_print_flags pageflag_names[] = {
+	{1UL << PG_locked,		"locked"	},
+	{1UL << PG_error,		"error"		},
+	{1UL << PG_referenced,		"referenced"	},
+	{1UL << PG_uptodate,		"uptodate"	},
+	{1UL << PG_dirty,		"dirty"		},
+	{1UL << PG_lru,			"lru"		},
+	{1UL << PG_active,		"active"	},
+	{1UL << PG_slab,		"slab"		},
+	{1UL << PG_owner_priv_1,	"owner_priv_1"	},
+	{1UL << PG_arch_1,		"arch_1"	},
+	{1UL << PG_reserved,		"reserved"	},
+	{1UL << PG_private,		"private"	},
+	{1UL << PG_private_2,		"private_2"	},
+	{1UL << PG_writeback,		"writeback"	},
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+	{1UL << PG_head,		"head"		},
+	{1UL << PG_tail,		"tail"		},
+#else
+	{1UL << PG_compound,		"compound"	},
+#endif
+	{1UL << PG_swapcache,		"swapcache"	},
+	{1UL << PG_mappedtodisk,	"mappedtodisk"	},
+	{1UL << PG_reclaim,		"reclaim"	},
+	{1UL << PG_buddy,		"buddy"		},
+	{1UL << PG_swapbacked,		"swapbacked"	},
+	{1UL << PG_unevictable,		"unevictable"	},
+#ifdef CONFIG_MMU
+	{1UL << PG_mlocked,		"mlocked"	},
+#endif
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
+	{1UL << PG_uncached,		"uncached"	},
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+	{1UL << PG_hwpoison,		"hwpoison"	},
+#endif
+	{-1UL,				NULL		},
+};
+
+static void dump_page_flags(unsigned long flags)
+{
+	const char *delim = "";
+	unsigned long mask;
+	int i;
+
+	printk(KERN_ALERT "page flags: %#lx(", flags);
+
+	/* remove zone id */
+	flags &= (1UL << NR_PAGEFLAGS) - 1;
+
+	for (i = 0; pageflag_names[i].name && flags; i++) {
+
+		mask = pageflag_names[i].mask;
+		if ((flags & mask) != mask)
+			continue;
+
+		flags &= ~mask;
+		printk("%s%s", delim, pageflag_names[i].name);
+		delim = "|";
+	}
+
+	/* check for left over flags */
+	if (flags)
+		printk("%s%#lx", delim, flags);
+
+	printk(")\n");
+}
+
+void dump_page(struct page *page)
+{
+	printk(KERN_ALERT
+	       "page:%p count:%d mapcount:%d mapping:%p index:%#lx\n",
+		page, page_count(page), page_mapcount(page),
+		page->mapping, page->index);
+	dump_page_flags(page->flags);
+}
--- linux-mm.orig/mm/memory.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory.c	2009-12-14 19:21:22.000000000 +0800
@@ -430,12 +430,8 @@ static void print_bad_pte(struct vm_area
 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
 		current->comm,
 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
-	if (page) {
-		printk(KERN_ALERT
-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
-		page, (void *)page->flags, page_count(page),
-		page_mapcount(page), page->mapping, page->index);
-	}
+	if (page)
+		dump_page(page);
 	printk(KERN_ALERT
 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
--- linux-mm.orig/mm/memory_hotplug.c	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/mm/memory_hotplug.c	2009-12-14 19:21:22.000000000 +0800
@@ -678,9 +678,9 @@ do_migrate_range(unsigned long start_pfn
 			if (page_count(page))
 				not_managed++;
 #ifdef CONFIG_DEBUG_VM
-			printk(KERN_INFO "removing from LRU failed"
-					 " %lx/%d/%lx\n",
-				pfn, page_count(page), page->flags);
+			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
+			       pfn);
+			dump_page(page);
 #endif
 		}
 	}
--- linux-mm.orig/include/linux/mm.h	2009-12-11 10:01:25.000000000 +0800
+++ linux-mm/include/linux/mm.h	2009-12-14 19:21:22.000000000 +0800
@@ -1328,5 +1328,7 @@ extern void shake_page(struct page *p, i
 extern atomic_long_t mce_bad_pages;
 extern int soft_offline_page(struct page *page, int flags);
 
+extern void dump_page(struct page *page);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

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Re: [PATCH] mm: introduce dump_page() and print symbolic flag names

[Américo Wang]

On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
>- introduce dump_page() to print the page info for debugging some error condition.

Since it is for debugging, shouldn't it be surrounded by
CONFIG_DEBUG_VM too? :-/

Thanks.


>- convert three mm users: bad_page(), print_bad_pte() and memory offline failure. 
>- print an extra field: the symbolic names of page->flags
>
>Example dump_page() output:
>
>[  157.521694] page:ffffea0000a7cba8 count:2 mapcount:1 mapping:ffff88001c901791 index:147
>[  157.525570] page flags: 100000000100068(uptodate|lru|active|swapbacked)
>
>CC: Ingo Molnar <mingo@elte.hu> 
>CC: Alex Chiang <achiang@hp.com>
>CC: Rik van Riel <riel@redhat.com>
>CC: Andi Kleen <andi@firstfloor.org> 
>CC: Mel Gorman <mel@linux.vnet.ibm.com> 
>CC: Christoph Lameter <cl@linux-foundation.org> 
>Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
>---
> include/linux/mm.h  |    2 +
> mm/memory.c         |    8 +---
> mm/memory_hotplug.c |    6 +--
> mm/page_alloc.c     |   83 +++++++++++++++++++++++++++++++++++++++---
> 4 files changed, 86 insertions(+), 13 deletions(-)
>
>--- linux-mm.orig/mm/page_alloc.c	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/mm/page_alloc.c	2009-12-16 20:17:18.000000000 +0800
>@@ -49,6 +49,7 @@
> #include <linux/debugobjects.h>
> #include <linux/kmemleak.h>
> #include <trace/events/kmem.h>
>+#include <linux/ftrace_event.h>
> 
> #include <asm/tlbflush.h>
> #include <asm/div64.h>
>@@ -262,10 +263,7 @@ static void bad_page(struct page *page)
> 
> 	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
> 		current->comm, page_to_pfn(page));
>-	printk(KERN_ALERT
>-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
>-		page, (void *)page->flags, page_count(page),
>-		page_mapcount(page), page->mapping, page->index);
>+	dump_page(page);
> 
> 	dump_stack();
> out:
>@@ -5106,3 +5104,80 @@ bool is_free_buddy_page(struct page *pag
> 	return order < MAX_ORDER;
> }
> #endif
>+
>+static struct trace_print_flags pageflag_names[] = {
>+	{1UL << PG_locked,		"locked"	},
>+	{1UL << PG_error,		"error"		},
>+	{1UL << PG_referenced,		"referenced"	},
>+	{1UL << PG_uptodate,		"uptodate"	},
>+	{1UL << PG_dirty,		"dirty"		},
>+	{1UL << PG_lru,			"lru"		},
>+	{1UL << PG_active,		"active"	},
>+	{1UL << PG_slab,		"slab"		},
>+	{1UL << PG_owner_priv_1,	"owner_priv_1"	},
>+	{1UL << PG_arch_1,		"arch_1"	},
>+	{1UL << PG_reserved,		"reserved"	},
>+	{1UL << PG_private,		"private"	},
>+	{1UL << PG_private_2,		"private_2"	},
>+	{1UL << PG_writeback,		"writeback"	},
>+#ifdef CONFIG_PAGEFLAGS_EXTENDED
>+	{1UL << PG_head,		"head"		},
>+	{1UL << PG_tail,		"tail"		},
>+#else
>+	{1UL << PG_compound,		"compound"	},
>+#endif
>+	{1UL << PG_swapcache,		"swapcache"	},
>+	{1UL << PG_mappedtodisk,	"mappedtodisk"	},
>+	{1UL << PG_reclaim,		"reclaim"	},
>+	{1UL << PG_buddy,		"buddy"		},
>+	{1UL << PG_swapbacked,		"swapbacked"	},
>+	{1UL << PG_unevictable,		"unevictable"	},
>+#ifdef CONFIG_MMU
>+	{1UL << PG_mlocked,		"mlocked"	},
>+#endif
>+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
>+	{1UL << PG_uncached,		"uncached"	},
>+#endif
>+#ifdef CONFIG_MEMORY_FAILURE
>+	{1UL << PG_hwpoison,		"hwpoison"	},
>+#endif
>+	{-1UL,				NULL		},
>+};
>+
>+static void dump_page_flags(unsigned long flags)
>+{
>+	const char *delim = "";
>+	unsigned long mask;
>+	int i;
>+
>+	printk(KERN_ALERT "page flags: %lx(", flags);
>+
>+	/* remove zone id */
>+	flags &= (1UL << NR_PAGEFLAGS) - 1;
>+
>+	for (i = 0; pageflag_names[i].name && flags; i++) {
>+
>+		mask = pageflag_names[i].mask;
>+		if ((flags & mask) != mask)
>+			continue;
>+
>+		flags &= ~mask;
>+		printk("%s%s", delim, pageflag_names[i].name);
>+		delim = "|";
>+	}
>+
>+	/* check for left over flags */
>+	if (flags)
>+		printk("%s%#lx", delim, flags);
>+
>+	printk(")\n");
>+}
>+
>+void dump_page(struct page *page)
>+{
>+	printk(KERN_ALERT
>+	       "page:%p count:%d mapcount:%d mapping:%p index:%lx\n",
>+		page, page_count(page), page_mapcount(page),
>+		page->mapping, page->index);
>+	dump_page_flags(page->flags);
>+}
>--- linux-mm.orig/mm/memory.c	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/mm/memory.c	2009-12-14 19:21:22.000000000 +0800
>@@ -430,12 +430,8 @@ static void print_bad_pte(struct vm_area
> 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
> 		current->comm,
> 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
>-	if (page) {
>-		printk(KERN_ALERT
>-		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
>-		page, (void *)page->flags, page_count(page),
>-		page_mapcount(page), page->mapping, page->index);
>-	}
>+	if (page)
>+		dump_page(page);
> 	printk(KERN_ALERT
> 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
> 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
>--- linux-mm.orig/mm/memory_hotplug.c	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/mm/memory_hotplug.c	2009-12-14 19:21:22.000000000 +0800
>@@ -678,9 +678,9 @@ do_migrate_range(unsigned long start_pfn
> 			if (page_count(page))
> 				not_managed++;
> #ifdef CONFIG_DEBUG_VM
>-			printk(KERN_INFO "removing from LRU failed"
>-					 " %lx/%d/%lx\n",
>-				pfn, page_count(page), page->flags);
>+			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
>+			       pfn);
>+			dump_page(page);
> #endif
> 		}
> 	}
>--- linux-mm.orig/include/linux/mm.h	2009-12-11 10:01:25.000000000 +0800
>+++ linux-mm/include/linux/mm.h	2009-12-14 19:21:22.000000000 +0800
>@@ -1328,5 +1328,7 @@ extern void shake_page(struct page *p, i
> extern atomic_long_t mce_bad_pages;
> extern int soft_offline_page(struct page *page, int flags);
> 
>+extern void dump_page(struct page *page);
>+
> #endif /* __KERNEL__ */
> #endif /* _LINUX_MM_H */
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Re: [PATCH] mm: introduce dump_page() and print symbolic flag names

[KOSAKI Motohiro]

> On Wed, Dec 16, 2009 at 08:26:40PM +0800, Wu Fengguang wrote:
> >- introduce dump_page() to print the page info for debugging some error condition.
> 
> Since it is for debugging, shouldn't it be surrounded by
> CONFIG_DEBUG_VM too? :-/

No.
typically, wrong driver makes bad_page() calling and MM developer suggested
how to fix in lkml. then, MM developer hope it is enabled on end user's
machine.

Thanks.


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